1. Field of the Invention
The present invention relates to an optical module included in a miniature camera using imaging elements, such as a charge-coupled device (CCD).
2. Description of the Related Art
In recent years, electronic devices, such as mobile phones and laptop computers that employ a miniature camera, are being provided. There is a great demand for miniaturization and weight-saving of these electronic devices. The downsizing and weight-saving of the cameras installed within these devices are also required. Thus, there is a need to further downsize the optical module which is an optical component of the camera.
With regard to the optical module, a configuration having a lens holder that holds a lens, a lens barrel that stores the lens holder to allow movement, a cylindrical cam that has a cam groove that engages with an engaging pin extending from a side surface of the lens holder and moves the lens holder in a light axis direction, and an actuator that drives the cylindrical cam has been conventionally implemented. Even in a miniaturized optical module, the basic structure described above is the same and these plural components must be assembled accurately. In the optical module installed in mobile phones and the like, in particular, it is vital that the cylindrical cam is disposed after the lens barrel is accurately positioned in relation to the CCD disposed on a circuit board, and in addition, that the actuator is disposed so that driving force is efficiently transmitted to the cylindrical cam, etc. In the miniaturized optical module, even a minuscule misalignment can cause degradation of a captured image, and thus, assembly has to be performed with care.
Japanese Patent Application Publication No. 7-63972 (hereinafter, referred to as Patent Document 1) discloses an optical module. In the Patent Document 1, a disposal relationship of a common lens barrel and actuator (motor) included in the optical module is shown. Conventionally, a method has been implemented, in which the lens barrel and the motor are constructed separately, and assembled and attached to a frame. This method also applies to the construction of the miniaturized optical module. The lens barrel and a miniature motor are constructed separately and joined on the circuit board, thus forming one optical module. When an assembly configuration as such is implemented, holes and pins for positioning or a guide pin for positioning are arranged on the circuit board and the motor is mounted in the predetermined position.
However, in the configuration in which the lens barrel and the motor are assembled and attached separately, the lens barrel is fixed to the circuit board first and the position of the lens barrel becomes the base. The position of the lens barrel is decided in relation to the CCD and fixed to the circuit board. Specifically, the lens barrel is disposed so that the CCD on the circuit board is in focus. However, in many instances, the position of the lens barrel becomes deviated from the planned position during the actual assembly and attachment operation. If a misalignment exceeds an acceptable error limit, the error must be corrected by adjustment of the lens barrel to the center of the CCD or adjustment of the position of lens barrel based on the outward form of the CCD.
When the configuration in which the lens barrel and the motor are composed separately and assembled and attached to the circuit board, as such, is implemented, the disposal position of the actuator is determined under the premise that the lens barrel is disposed in the predetermined position on the circuit board. However, the position of the lens barrel often becomes out of alignment during the actual assembly and attachment. If the position of the lens barrel is misaligned as such, the position of the cylindrical cam set in the lens barrel also becomes misaligned. As a result, a situation occurs in which relative positions of the cylindrical cam and the motor are out of the designed range. The optical module that has been out of alignment during assembly cannot efficiently transmit the driving force of the motor to the cylindrical cam-side and cannot maintain predetermined capability.